Important basic types of monochromators, in which only one color of a spectrum is masked out, and polychromators in which entire spectral ranges are recorded simultaneously with the aid of large-area receivers, such as photographic plates or receiver arrays, are described in J. A. Samson, "Techniques of Vacuum Ultraviolet Spectroscopy" New York, Wiley 1967, or also in W. Werner, "Imaging Properties of Diffraction Gratings" Thesis, Uitgeverij Waltman, Delft, 1970.
In monochromator systems it is known that a large-area planar or curved receiver can stand at the location of the exit slot. An entire spectrum can be projected onto that receiver in the same manner as in the case of a polychromator. Such an apparatus is, for example, the polychromator described in German Patent No. 2,829,802 (G 01 J, 3/18), in which another part of the spectrum appears on a planar receiving line if an appropriately corrected holographic concave grating, which throws an image of the entry slot on this receiving line, is rotated about a vertex. Other polychromators based on concave gratings are disclosed, for example, in German Patent No. 2,656,119 (G 01 J, 3/18), East German Patent No. 251,837 (G 02 B, 5/32), U.S. Pat. No. 4,568,187 (G 01 J, 3/20), and European Patent No. 156,232 (G 01 J, 3/18).
In Soviet Patent No. 1,358,538 (G 01 J, 3/18) there is disclosed a spectrograph based on a corrected holographic concave grating in the immediate surroundings of the Rowland circle, in which the curved spectrum developing in the vicinity of the Rowland circle is adapted to a planar receiver by using an image field flattening lens.
All of the methods used heretofore are either corrected with low resolution on a flattened image field, or are aligned with higher resolution on a curved image field. A curved image field, however, is not adapted to the flat receiver line that is technologically easy to make. The image field flattening lens described in Soviet Patent No. 1,358,538, set close in front of the receiver, has the disadvantage that it is illuminated at an angle in well corrected grating arrangements, and thus leads to slanting beam aberrations with the technologically necessary lens thickness. Furthermore, the flattening lens directly in front of the receiver line produces an increase in the stray and false light content within the spectrum.